Heat responsive means for blade cooling



D. J. MCCARTY ET AL 2,906,494

HEAT RESPONSIVE MEANS FOR BLADE COOLING Filed June 12, 1956 Sept. 29, 1959 IN V EN TOR. @fyo Jan;-

United States A Patent HEAT RESPONSIVE MEANS FOR COOLING Application June 12, 1956, Serial No. 591,002 1 Claim. 01. 253-391 BLADE This invention relates to means of controlling the local temperatures in turbines.

In order to insure the maximum efliciency of any turbine, gas or steam, it is necessary that the turbine operate at a constant uniform temperature. Solid type blading is often used in a turbine where the maximum temperature of the passing gas or steam is not too high. However, in modern day turbines, the temperatures of the fluids passing through the turbine are very high and cooling means for the various parts of the turbine must be provided to reduce the temperature thereof. Even with such cooling means, hot spots develop, due to the very high temperatures of the passing fluids, in isolated I sections of the turbine that are difficult to cool.

A further disadvantage occurs with the cooling systems presently in use in that the amount of cooling is kept constant and no automatic compensation is made for differences in temperature between the blading and the passing fluids. As a result of this, at times the turbine runs at something less than maximum eificiency.

An object of this invention, therefore, is a cooling system for turbines wherein the danger of hot-spots is eliminated.

A further object of this invention is a system wherein a turbine runs at maximum efiiciency by operating at a constant temperature under varying conditions.

A still further object of this invention is a cooling system which automatically controls the amount of cooling fluid passing through the hot turbine.

These and additional objects will be readily apparent to those skilled in the art from a perusal of the following disclosure and an examination of the enclosed drawings wherein:

Figure l is a cross-sectional view of a turbine showing the details of the cooling systems,

Figure 1A is a cross-sectional view of a fragment of a turbine complementary to that of Figure 1 showing a modification of the invention,

Figure 2 is a modification of the location of the cooling system control unit,

Figure 3 is a modification of the cooling system control unit and valve,

Figure 4 is a cross-sectional view along section lines 44 of Figure 1, and

Figure 5 is a further modification of the coling system control unit.

In Figure 1, a turbine 1 comprises a solid rotor, 2, having on its periphery a plurality of blades 4. Encompassing the turbine is a casing 3 providing a housing for the turbine rotor and means for suspending the stator blades.

Forward and rear rotor blades 4 are hollow, which construction is well known. Forward blades 4 are divided by a transverse wall 5 commencing from the root of the blade and terminating justshort of the tip 44 thereby dividing the blade into two compartments, 46 and 47, with an open passage 48 at the tip joining the compartments.

Within each blade a build up portion 6, extending from ithe roof, has a plurality of ports 6 therein; one port for each compartment. I

A bimetallic leaf 8 is secured at its mid-point to the wall 40 and extends over both ports. A coolant feed line 41 leads into one of the compartments via passage 14 and return line 42 is connected to the other of the com partments via passage 13. Y 1.

In the stator blade 21 preceding the above turbinerotor stage, the blades are secured to shroud ring 27 and to the inner ring 43. The blade is divided into two corn.- partments by a transverse partition 22 in which is provided a passage 23. The port is covered by a bimetallic strip 24 fastened at one end to the partition wall. A conduit 15 feeds cooling fluid into one of the compartments while conduit 16 returns the fluid back to the source.

A further modification of the valve means is shown in Figure 1A. In the rotor blade 4 a partition wall 12 divides the blade into two compartments, 49' and 51, with a passageway 52 at the tip, 44, of the blade conmeeting the compartments, while in the stator stage, blade 21 has a partition wall 25 dividing the blade into two similar compartments. Conduits 17 and 18 lead into the compartments at the root of the stator .blade; conduits 9 and 10'lead into thecor'npartments at the root of the rotor blade. Both compartment entry ports are covered by a bimetallic element, element 11 in the rotor blade and element 26 in the stator blade. Each element is connected at its mid-point to its respective partition wall and its respective blade root 56 and 59.

Figure 2 illustrates a further modification of the valve means. Conduit 19 feeds in and conduit 20 feeds from the compartments 54 and 55, respectively; recessed adjacent an opening of one of the compartments is a bimetallic element 28; the other opening is not serviced with a bimetallic element and fluid passes freely through the port.

In Figure 3 a further modification of the valve means is shown. The blade root or shroud ring has attached thereto the bimetal element 29 via a rivet 33. Feed line 32 terminates in a countersunk section 31 and a matching truncated nipple or valve element 30 is fastened to the portion of the bimetal element 29 covering the port. When the opening is closed, recess 31 accommodates valve element 30 preventing a passage of fluid; when the valve is open, elemnet 30 is clear of the recess 31 providing an opening for the passage of fluid.

Figure 5 shows still a further modification. In this figure, conduits 36 and 37 are connected to the two compartments 57 and 58. Valve 50 is maintained in its recess by the action magnet 34. When the temperature of the fluid increases, the magnet loses some of its retaining properties and the spring 35 forces the valve 50 to its open position.

The cooling fluid may be connected to any type of cooler 38 well known in the art or it may be directed externally of the turbine to atmosphere if the fluid is air.

Operation All of the modifications illustrated except that of Figure 5 operate basically in the same manner. If the temperature of the cooling fluid is low, the bimetallic element in each of the modifications covers the fluid inlet ports or the element covers both the inlet and outlet ports.

When the temperature of the cooling fluid starts to increase above a predetermined range of temperatures, the bimetallic valve slowly starts to turn thus slowly uncovering the associated passage. A similar action occurs if a hot spot begins to develop in one of the blades. The bimetallic element/s of that blade further open the valve allowing additional cooling fluid to circulate through the blade, thus cooling it more than the adjacent blades.

In a steady state condition, the valves are partially open allowing a percentage of maximum flow to go through. If the blades begin to heat up, the bimetallic valves open further allowing additional fluid to pass through; if the blades tend to cool somewhat, the bime allie valves tend to close thereby restricting the fiow of fluid and the blades have a tendency to return to the temperature of the steady state condition.

In the modification of Figure 5, the magnet 34 functions in a manner similar to the bimetallic valve. The 'magnetic action fluctuates under the action of the heated fiuid thereby allowing the bias action of the spring to come into play.

While several modifications of the basic temperature control system are shown in Figure 1, it is of course understood that one type of valve means may be used for both the stator and rotor blades or the blades of the rotor may have one type of bimefal and valve and the blades of the stator have another modification of the bimetal and valve.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claim the invention may be practiced otherwise than as specifically described.

What is claimed is:

In a turbine having a hollow fluid cooled blade, said blade having a root portion and a tip portion, a wall in the hollow of said blade extending longi.udinally from the root to a point short of the tip thereby forming two compartments with fluid communication between them, said blade having an inlet opening in its root portion providing fluid access into one of said compartments and an outlet opening in its root portion providing a fluid exit from the other of said compartments, and a bimetallic leaf valve in said blade extending through said parti.ion wall for normally covering said openings and secured intermediate its ends to the blade root portion and free at its ends to permit turning of said leaf at its free ends away from said blade root portion with increased temperature thereby uncovering the openings for cooling fluid flow through the blade.

References Cited in the file of this patent .UNITED STATES PATENTS 

